If it was voluntary opt in then then you'd just click away once and that would be the sign that you didn't voluntarily opt in.
Voluntary opt in can work together with targeted ads:
- the customer can opt in to receive more relevant ads (hopefully). A note on the page with an explanation and a way to actively choose targeted would probably be OK with me and I guess some people would choose it.
- or the customer ignores the notice and get general or hopefully contextual ads
The current in-your-face-and-defaults-to-track-if-you-follow -the-defaults system however is not voluntary and not opt in IMO.
My guess is: They are not happy. They accept it because a lot of effort is put in dark patterns to make it seem unavoidable.
Also a lot of effort seems to have been put into making the opt-in alternative the default - to the point where I'm not comfortable calling it opt-in any more.